Nutrasweet News: It Turns Nutrabitter If Left Out In The Heat

If you store your low-calorie soft drinks in an overheated garage, drink them quickly.

NutraSweet, the artificial sweetener used in more and more diet soft drinks, decomposes if it sits for long in temperatures above 85 degrees.

Bitter soft drinks may be the only result. But some consumer groups suggest the chemical byproducts of the breakdown could be harmful.

Manufacturers acknowledge that aspartame decomposes under high temperatures, but they are unconcerned.

''It cannot be stored in a non-air-conditioned place for more than six weeks,'' said Jesse Meyers, publisher of Beverage Digest, a trade newsletter. ''But since soft drinks are consumed generally within two weeks of production, there's no problem.''

Sometimes, though, people stock up on drinks at sales; sometimes the home supply hangs around for a while, when the family goes on vacation.

''Assuming a temperature of 90-plus degrees, which is not unrealistic, when you took your first taste, you would immediately look at the glass or bottle and say, 'What's wrong with this?' You certainly would not continue to consume it, because it would not taste good,'' said Dr. Paul Kifer, head of Oregon State University's department of food science and technology and a spokesman for the National Soft Drink Association.

Kifer also said scientific studies have shown that aspartame taken at ''reasonable levels'' is ''no cause for concern.'' But what's a safe or reasonable level?

''It's determined by the capacity of your system. You can only drink so much fluid in a day, and really a soft drink is 80 to 90 percent water.''

In November the federal Centers for Disease Control reported the results of its investigation of nearly 600 consumer complaints about aspartame's side effects. The complaints ranged from headaches, dizziness and mood alterations to changes in menstrual patterns. Most of the complaints were mild, said the agency, concluding there were no ''serious, widespread, adverse health consequences attendant to the use of aspartame.'' Some people, however, might be ''unusually sensitive to the product.''

''It is by far the most incredibly well-researched additive that we have had since Eve started to hand out apples,'' Meyers said. ''Some 30 governments have looked into the safety of aspartame and each has said it comes up with a clean bill of health with small caveats.''

Two caveats: Do not store the product in a warm place. Sufferers of phenylketonuria (PKU), a rare, hereditary disease of metabolism, should avoid all products containing aspartame.

All newborns are tested for the condition, which affects one in 15,000 people nationwide. A Boston Children's Hospital physician, writing in The New England Journal of Medicine, suggests pregnant women avoid aspartame because they might damage the brains and IQs of their unborn children. The Food and Drug Administration and aspartame-manufacturer G.D. Searle and Co. reject that idea.